Democrat state Sen. Daniel Mongiardo's bid to unseat Kentucky U.S. Sen. Jim Bunning suffered an apparent setback Tuesday with the abrupt resignation of his campaign manager.

In an e-mail sent to Democrats across the state Tuesday morning, Jody Lassiter said he is leaving the Mongiardo campaign "due to my strong difference of opinion concerning management of staff and the resulting direction of the campaign."

He declined to elaborate on their disagreement. Lassiter said he did "not want to exercise a public dispute" with Mongiardo, and that they had resolved their differences privately.

"This is a matter which is not for public discussion and I'm not going to engage that," he said. "This was a matter of personal differences of opinion and I felt I could no longer continue to be effective for him as campaign manager."

Mongiardo, a state senator from Hazard in eastern Kentucky, said Lassiter has "decided to pursue a different career direction."

"I very much appreciate his service to my campaign, and we all wish him only the best," Mongiardo said in a statement.

Lassiter lives in Shelbyville and had been commissioner of the Department for Local Government in former Gov. Paul Patton's administration. He had been with the campaign just five weeks.

"I've talked to people in and close to the campaign and (Lassiter) never really immersed himself into the campaign," said Kenton County Democratic Party Chairman Nathan Smith.

Bunning's Fort Wright campaign office issued a brief statement saying that the Republican senator from Southgate "is focused on the issues and delivering for Kentucky."

Mongiardo's campaign office refused to comment on speculation from Republicans that Lassiter's departure is a precursor to Mongiardo dropping out of the race.

But the campaign privately told Northern Kentucky Democrats Tuesday that Mongiardo has no intention of leaving the race despite trailing Bunning by more than $3 million in campaign funds.

Kenton County GOP Chairman Greg Shumate said Lassiter's departure "is a signal that the campaign isn't getting any legs."

Smith said changing campaign managers is not always a bad idea or a sign of political weakness, particularly when the general election is still seven months away.